1. Field of the Invention
The present invention relates to a mechanical component, a mechanical component manufacturing method, a movement, and a timepiece.
2. Description of the Related Art
A precision machine such as a mechanical timepiece employs a mechanical component such as a cogwheel, which rotates around a shaft member.
As a connection structure between a mechanical component and a shaft member, there exists a structure in which a forcing-in portion formed of metal is formed at a through-hole of the mechanical component, with the forcing-in portion being forced into the forcing-in portion (See, for example, JP-A-11-304956 (Patent Literature 1)).
A mechanical component of this type is formed thin, so that it is subject to the influence of stress generated when the shaft member is forced in; however, the mechanical component having the forcing-in portion can mitigate the stress due to the forcing-in portion.
In the mechanical component disclosed in Patent Literature 1, a metal film is formed over the entire surface through plating, and, of this metal film, the portion formed on the inner surface of the through-hole can function as the forcing-in portion mitigating the stress due to the forcing-in of the shaft member.
However, the above mechanical component, in which the metal film on the inner surface of the through-hole is formed by plating, has the following problems:
When the metal film is thin, the plastic deformation amount of this metal film is small, and, in particular, when a brittle material (such as a ceramic material) is used for the mechanical component, the component is subject to breakage. Further, the metal film has the possibility of being separated from the inner surface of the through-hole. The separation of the film can cause axial deviation. Further, the mechanical component of the above structure is subject to rotation looseness.
Further, the metal film is formed over the entire surface of the mechanical component, so that, when the metal film on the inner surface of the through-hole is made thick, the outer diameter of the mechanical component increases; thus, there is a fear of its relationship with other mechanical components being adversely affected.